A conventional component mounting apparatus and a conventional component mounting method using the component mounting apparatus are described.
As shown in FIG. 3B, a component mounting apparatus 30 generally comprises: a rotating table 7; an X-Y table 3; a component feeder 4; a component feed section 5 to which the component feeder 4 is removably equipped; a rotating-table driver 8 for driving the rotating table 7; a table driver 9 for driving the X-Y table 3; a component-feeding-section driver 10 for driving the component feed section 4; and a component-mounting controller 20 for performing operational control of drivers 8, 9, 10.
The rotating table 7, of which a table body 7a will not move, has suction nozzles 2 which move on a move path along the periphery of the table body 7a and which serve for mounting electronic components 11 onto a printed board 1. The suction nozzles 2 are moved by the rotating-table driver 8 between a component holding position which is one place on the move path and at which the holding of an electronic component 11 is performed, and a hold releasing position which is another place on the move path and at which the holding of the component is released. Moreover, the suction nozzles 2 will move up and down to suck up and mount electronic components. The X-Y table 3, which is located below the rotating table 7, has the printed board 1 placed thereon. Then, for the mounting of an electronic component 11 (which has been transferred to the hold releasing position by a suction nozzle 2) on to the printed board 1 at a component mounting position, the X-Y table 3 moves the printed board 1 so that the component mounting position and the hold releasing position coincide with each other. It is noted that the X-Y table 3 is moved by the table driver 9 in X and Y directions as shown in the figure. The component feeder 4 has a plurality of component accommodating units 4a for accommodating therein a plurality of types of electronic components 11, respectively. The accommodating units 4a are arrayed along the component feed section 5 in a Z direction, as shown in the figure, corresponding to the direction in which the component feeder 4 is moved. The component feeder 4 of such arrangement is moved in the Z direction by the driver 10 so that the electronic component 11 to be mounted is positioned at the component holding position. It is noted that the X, Y and Z directions are within the same plane and that the X and Z directions are parallel to each other.
In the component mounting apparatus 30 as described above, the electronic component 11 is taken out from the component feed unit 4a at the component holding position by the suction nozzle 2, and during the transfer to the hold releasing position, the posture of the electronic component 11 is detected by a recognizer 6. Then, based on the detection result, the electronic component 11 during transfer is corrected in position, and transferred to the hold releasing position. Meanwhile, the X-Y table 3 moves in the X, Y directions so that the component mounting position on the printed board 1 at which the electronic component 11 is to be mounted becomes coincident with the hold releasing position. Accordingly, at the hold releasing position, the suction nozzle 2 mounts the electronic component 11 at the component mounting position on the printed board 1. Further, the printed board 1 is also positionally corrected, as required, by detecting a mark provided on the printed board 1 with the recognizer 6.
Indeed, occurrence of errors in such a component mounting apparatus 30 have been on the decrease with the technical progress of the mounting equipment. However, for the exhaustion of electronic components to be mounted or the occurrence of errors, it has been the case that the operator takes measures of electronic component replenishment or error cancellation upon each occurrence of an error, or of feeding components by the component feeding method as disclosed in Japanese Patent Laid-Open Publication No. 60-206098 or No. 62-21300, by which the production of circuit boards is continued.
Next, the arraying of the electronic components 11 onto the component feeder 4 as well as the decision of a mounting sequence according to the prior art are described with reference to FIGS. 4 and 5. For example, as shown in FIG. 4, assume that 3 pieces of electronic components A, 2 pieces of electronic components B and 1 piece of electronic components C are to be mounted onto the printed board 1. In such a case, according to a flow chart as shown in FIG. 5, first at Step (represented by "S" in the figure) 1, electronic components are classified into groups according to mounting cycle time, which is the time necessary from when one electronic component is taken out from the component feeder 4 until it is mounted onto the printed board 1. Thus, the electronic components are classified into groups having the same mounting cycle time, respectively, and then the groups, are put into an ascending order of the mounting cycle times. In this example, the electronic components A and B have a mounting cycle time of 0.1 second, and the electronic components C have a mounting cycle time of 0.2 second, so that the resulting order of array is A.fwdarw.B.fwdarw.C.
Subsequently at Step 2, based on the processing of Step 1, it is decided which electronic components are placed at the individual component accommodating units 4a located at Z1, Z2, . . . in the component feeder 4. In this example, the electronic components A are placed at Z1, the electronic components B are placed at Z2 and the electronic components C are placed at Z3.
Subsequently at Step 3, an optimization of the mounting sequence is executed based on the processing of Step 2, by which the mounting sequence is decided. In this example, the mounting operation is carried out in a sequence as indicated by arrows within the printed board 1 as shown in FIG. 4. That is, the electronic components A are mounted in an order of a component mounting position N1 to a component mounting position N2 to a component mounting position N3, respectively. Then electronic components B are mounted in an order of a component mounting position N4 to a component mounting position N5, respectively. Finally, an electronic component C is mounted to a component mounting position N6.
The placement of electronic components onto the component feeder 4 as well as the mounting sequence of the electronic components according to the prior art have been determined by such method and procedure as described above. In the above example, the electronic components A set in the Z1 component accommodating unit include 3 pieces, the electronic components B set in the Z2 component accommodating unit include 2 pieces and the electronic component C set in the Z3 component accommodating unit includes 1 piece.
In addition, the operations of Steps 1 to 3 are carried out by the component-mounting controller 20 executing arithmetic operations with the feed of information as to the types of electronic components to be mounted. In other words, controller 20 uses information on the electronic components A, B, C as well as information on the quantities of the individual types of electronic components to be mounted in this example. Information as to the mounting cycle time may be previously stored in the component-mounting controller 20 for each type of electronic component, or otherwise the information may be fed from time to time as required.
However, with the conventional method as described above, the number of electronic components to be mounted on the printed board 1 differs from type to type of electronic components. In other words, the number of electronic components A is 3, the number of electronic components B is 2 and the number of electronic components C is 1. As the three types of electronic components A, B, C are involved in the above example, the electronic components to be mounted on the printed board 1 are arrayed in the component feeder 4 according to the types of electronic components. Therefore, the rate of consumption of electronic components that have been arranged in the component feeder 4 varies depending on the type of electronic components mounted on the printed board 1. Therefore, component exhaustion in the component feed section 5 will randomly occur during the production of the printed board 1. In the above example, 3 pieces of electronic components A are consumed for one printed board 1. If such production of printed boards 1 is continued, an exhaustion of electronic components A will occur first among the electronic components A to C fed to the component feeder 4, and an exhaustion of electronic components B will occur after a while, and an exhaustion of electronic components C will occur after another while.
Such rates of component exhaustion would cause the printed board 1 not to be completed, so that the whole component mounting apparatus would result in a halt each time a component exhaustion has occurred. This would cause an increase in the apparatus halt time involved in the component replacement work. In order to overcome such circumstances, there has been a disadvantage that the operator must monitor the equipment at all times during the operation of the component mounting apparatus.